Antenna Wire

There happens to be a lot of fuss out there about antenna wire. Most amateur radio shops sell «special» antenna wire at unreasonably high price, whilst most of the claims made about these wires are untrue. The situation reminds me a bit of the many loadspeaker cable myths. However, a less expensive and even better alternative exists.

For all my wire antenna projects I always use extremely flexible and comparatively cheap black-coloured 4mm² tinned HO7 V-K 4 wire. HO7 V-K 4 is the European wire harmonisation code. Rather unfortunately, this harmonisation code did not foresee a means of specifying the property of being "tinned". So, make sure to specify "tinned" when ordering this wire! In Belgium, the country of its original manufacturer, tinned HO7 V-K 4 is more commonly known as «VOBst 4 carré».

Tinned HO7 V-K 4 is a 4mm² wire made out of 51 tinned-copper braided strands and insulated with a 0.8mm thick layer of soft PVC. Tinned HO7 V-K wire is also available in other thicknesses, the last figure in the wire code indicating the conductor area in mm². See table and spec sheets for more information:

• HO7 V-K spec sheet (PDF)
• VOBst spec sheet (PDF)
  

The tinned-copper braided strands are what make the wire so extremely flexible. The tin around each of the copper strands makes soldering of the wire a breeze and prevents the copper from oxidating. After all, VOBst wire is designed for use in bathrooms! Nevertheless, I always make sure to cap the wire ends with a dot of clear glue to prevent moisture from entering through capillary action. It is better to be safe than sorry!

The 0.8mm thick black-coloured soft PVC insulating sheet is perfectly UV-resistant, so it will withstand exposure to sun rays. For those of you who would like to model their wire antennas with EZNEC, the only data I have found for the relative permittivity ε_r of soft PVC is the wide range of 4.0 to 8.0^[1]. The 4nec2 online manual mentions a range of 4.0 to 5.0 without quoting any reference. A value of ε_r = 5 will be a plausible estimate for most PVC-insulated wires.

I especially like this wire because it is relatively cheap, available on order from most vendors of electric installation material, very flexible but also very strong and most importantly it will not corrode in a wet and salty environment. It is a wire type that was invented here in Belgium and is used in bathrooms and on board of ships.

I have been operating my antennas for many years now without any issues despite some severe weather, salt and strain exposure. Of course, be sure to leave some sag when hanging up wire antennas. Check out Owen Duffy's, VK1OD, antenna wire catenary calculator to know how much sag for your particular situation.

I am not selling this wire! You probably will have to order this cable from your local electric hardware store, but most European stores will be able to get it for you without much delay.

To give you an indication of its price: In November 2006 I bought from a wholesaler 100m VOBst 4mm² for €66.33 (incl. VAT) and 100m of the lighter 2.5mm² VOBst for €40.35 (incl. VAT).

On a final note; Most of NEC-2-based antenna modelling programs (e.g. 4nec2 and EZNEC) can model insulated wires. Please, refer to the respective user manuals and L. B. Cebik about modelling insulated wires with NEC-2.